Acrylic synthetic fibers having novel structure

ABSTRACT

ACRYLIC FIBERS CONTAINING AT LEAST 85 MOLE PERCENT OF ACRYLONITRILE AND HAVING A UNIQUE STRUCTURE REPRESENTED BY AN X-RAY DIFFRACTION INTERFERENCE INTENSITY RATIO   OF 0.30 TO 0.70 HAVE A DURABLE WOOL-LIKE WAXY AND SOFT FEELING. THESE FIBERS ARE PRODUCED BY HETEROGENEOUSLY COPOLYMERIZING ACRYLONITRILE WITH AN ACRYLATE HAVING A LONGCHAIN ALKYL GROUP WITH 10-18 CARBON ATOMS IN A SOLVENT WHICH DISSOLVES THE ACRYLONITRILE BUT DOES NOT DISSOLVE THE A BLEND OF THE SAID SOLUTION AND A SOLUTION OF AN ORDINARY ACRYLONITRILE COPOLYMER. THE ACRYLATE SHOULD BE PRESENT IN AN AMOUNT OF 2-10 MOLE PERCENT IN THE ACRYLIC FIBER.

9 'HHRQfiHl MOTANI ETA!- ACRYLIC SYNTHETIC FIBERS HAVING NOVEL STRUCTURE Filed April 22, 1968 2 Sheets-Sheet 1 mama-u AOTMNI mm mwmm mom-113m .m'mmc FIBERS mum NOVEL STRUCTURE Filed. April 19m 12 Sheets-Sheet 3 US. Cl. 260-898 6 Claims ABSTRACT OF THE DISCLOSURE Acrylic fibers containing at least 85 mole percent of acrylonitrile and having a unique structure represented by an X-ray diffraction interference intensity ratio Meridian interference intensity at =21 Equator line interference intensity at, 20: 17

of 0.30 to 0.70 have a durable wool-like waxy and soft feeling. These fibers are produced by heterogeneously copolymerizing acrylonitrile with an acrylate having a longchain alkyl group with 1018 carbon atoms in a solvent which dissolves the acrylonitrile but does not dissolve the acrylate, and spinning the resulting solution; or spinning a blend of the said solution and a solution of an ordinary acrylonitrile copolymer. The acrylate should be present in an amount of 210 mole percent in the acrylic fiber.

This invention concerns acrylic synthetic fibers having a Wool-like hand, and more particularly novel acrylic synthetic fibers having a waxy and soft feeling similar to Wool because of their unique structure not seen in the conventional acrylic fibers.

Hitherto, acrylic fibers, because of their bulkiness, have been evaluated as fibers similar to wool, and have chiefly found applications in fields where wool is much used. In fact, however, the acrylic fibers are very coarse and stiff and have a feeling of creaky and coarse touch, thus lacking in a feeling of waxy and soft touch. With a view, therefore, to improving the surface touch of acrylic fibers, softening treatment by means of an oil preparation has generally been carried out. Cationic surface active agents have been much used particularly for imparting a woollike waxy feeling to the acrylic fibers, and tentative effects have been achieved by such treatment. When such treatment only results in the deposition of the oil preparation onto the surface of the fibers, the oil preparation will easily come off during a scouring or dyeing operation or Washing after the fibers have been made into end products, making it impossible to obtain durable effects. To remove such defects, improved methods have been considered and commercialized in which an oil preparation is impregnated into fibers in a swollen state, or it is added to a spinning solution comprising an acrylic polymer, but have been unable to give fibers having a satisfactory woollike feel.

Accordingly, it is an object of 'theinvention to provide acrylic fibers having a durable, closely wool-like feeling. Another object of the invention is to provide novel acrylic fibers which have a unique structure, and therefore, have a feeling of waxy and soft touch.

The acrylic fibers of the invention contain at least 85 mole percent of acrylonitrile and have an X-ray diffraction interference intensity ratio (to be referred to as LR. hereinafter) defined by of from 0.30 to 0.70 in their X-ray diffraction pattern.

nited States Patent 0 3,597,501 Patented Aug. 3, 19711.

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In the accompanying drawings:

FIG. 1 shows photographs of X-ray diffraction patterns indicating the difference in structure between the acrylic fibers of the invention and ordinary acrylic fibers;

FIG. 2 shows phase contrast microscopic photographs indicating the difference in structure between the abovementioned two types of acrylic fibers; and,

FIG. 3 shows X-ray diffraction. pattern photographs of acrylic fibers containing as a copolymer component an acrylic acid ester of a higher alcohol having a different number of carbon atoms.

The characteristic feature of the invention is that the acrylic fibers have an IR. of from 0.30 to 0.70. Acrylic fibers having such characteristic structure have not been known heretofore. In the conventional ordinary acrylic fibers, interference is seen only in the vicinity of 20:17 in the direction of equator line, but no meridian interference at 20:21 appears.

Because of the structure as specified by the abovementioned X-ray diffraction pattern, the acrylic fibers of the invention have a feel very similar to wool, above all, a wool-like waxy and soft feel. Since this feel is based on the structure of the fibers themselves, it is durable and does not disappear even by such operation as dyeing, scouring and washing.

When the LR. is less than 0.30, acrylic fibers do not exhibit a sufficient waxy and soft feeling. If, on the other hand, the LR. is larger than 0.70, the acrylic fibers have an excessive waxy and soft feeling, and become gluey with a decrease in tenacity. Thus, such acrylic fibers cannot be offered for practical use.

One method of manufacturing the acrylic fibers of the present invention having such unique structure is a copolymerization method which comprises heterogeneously polymerizing acrylonitrile with a monoethylenic ester containing a higher alkyl group (hereinafter to be referred to as a higher alkyl acrylate) expressed by the general formula wherein R is a hydrogen atom or a methyl group; R is an alkyl group having 10 to 18 carbon atoms, in the presence of a polymerization catalyst in a solvent which completely dissolves acrylonitrile but does not dissolve the higher alkyl acrylate to thereby form a copolymer comprising at least mole percent of acrylonitrile and 210 mole percent of a higher alkyl acrylate, and spinning a solution of the resulting copolymer.

We have made various studies about the above-mentioned procedure of copolymerization, and found the following facts.

(1) The meridian interference at 20:2l is due to an acrylate of the above-mentioned Formula 1 having a long-chain alkyl group with l0l8 carbon atoms. Acrylates having an alkyl group with less than 10 carbon atoms do not give a meridian interference at 20:21".

(2) In order for the resulting fibers to have an I.R. of 0.300.70, it is necessary that even the copolymerization of acrylonitrile with an acrylate of Formula 1 having an alkyl group with 10-18 carbon atoms should occur in a way close to that of block-copolymerization, and consequently, the arrangement of monomers in the copolymer should be similar to that of a block copolymer. A random copolymer obtained by an ordinary homogeneous solution-polymerization exhibits little meridian interference at 20:21.

(3) The above-mentioned copolymer having a structure similar to that of a block copolymer can be obtained When the solution (A) and solution (B) were mixed so that the stearyl acrylate might be 1 mol percent and the same operations were carried out, the obtained fibers had an X-ray interference intensity ratio of 0.14 and a uS.,ud. value of 0.102. It was thus impossible to obtain the intended waxy and soft feeling.

EXAMPLE 5 A copolymer solution (B) was prepared by heterogeneously polymerizing 70 mole percent of acrylonitrile, and 30.0 mole percent of an ester of vinyl alcohol and stearic acid under the same conditions as in Example 1. When this solution was spun, the obtained fibers completely glued with each other, and did not show any fibrous form.

The copolymer solution (B) was mixed with a solution (A) of a polymer obtained by reacting 93.5 mole percent of acrylonitrile, 6.0 mole percent of methyl acrylate and 0.5 mole percent of sodium allylsulfonate under the same conditions as employed in the preparation of solution (A) in Example 4, so that the ester of vinyl alcohol and stearic acid might be 3 mole percent based on the total amount of the polymer. The resulting mixture was spun into a 60% aqueous solution of dimethyl sulfoxide so that the final monofilament denier of the fibers might be 3, drawn to 6 times the original length, washed with water, and dried. There were obtained fibers having a tenacity of 3.4 gfd. and an elongation of 28%. The fibers had an X-ray interference intensity ratio of 0.44, and a ,u.s.,ud. value of 0.067.

When the above solution (A) alone was spun, the resulting fibers had an X-ray interference intensity ratio of 0, and a ,uS.-,ud. value of 0.110, showing a very remarkably creaky and coarse feeling.

We claim:

1. A process for the production of an acrylic fiber having at least 85 mole percent of acrylonitrile and having an X-ray diffraction interference intensity ratio defined by Meridian interference intensity at 20=2l Equator line interference intensity at 20=17 of from 0.30 to 0.70, which process comprises heterogeneously copolymerizing acrylonitrile with a monoethylenic ester of formula wherein R represents a hydrogen atom or a methyl group; and R represents an alkyl group having 16 to 18 carbon atoms, in a solvent which completely dissolves the acrylonitrile but does not dissolve said monoethylenic ester, in the presence of a polymerization catalyst, to thereby form a copolymer comprising at least mole percent of acrylonitrile and 2-10 mole percent of said monoethylenic ester, and thereafter spinning a solution of said copolymer.

2. The process of claim 1 wherein the monoethylenic ester is stearyl acrylate.

3. The process of claim 1 wherein the solvent is dimethyl sulfoxide.

4. The process of claim 11 wherein the polymerization catalyst is azobisisobutyronitrile.

5. A process for the manufacture of acrylic fibers having an X-ray ditfraction interference ratio defined by Meridian interference intensity at 20=21 Equator line interference intensity at 20 17 of from 0.30 to 0.70 which comprises spinning a mixture of (A) a solution of a homopolymer or copolymer of aclylonitrile, and (B) a solution of a copolymer obtained by heterogeneously copolymerizing acrylonitrile with a monoethylenic ester having a higher alkyl group expressed by the following formula References Cited UNITED STATES PATENTS 3,299,018 1/1967 lFreedman et al. 26085.5 3,060,157 10/1962 Goodman et a1. 260-793 2,846,559 8/1958 Rosenberg 219-46 2,436,926 8/1943 Jacobson 260-84 2,958,670 11/1960 Hare 260-326 SAMUEL H. BLECH, Primary Examiner C. J. 'SECCURO, Assistant Examiner US. Cl. X.R.

Fibers are wound around a cylinder having an outer diameter of 8 mm. so that they may be in parallel to the axis of the cylinder. A fiber taken from the same sample, and a prescribed load T is mounted on both ends of the fiber. This fiber is then hung over the cylinder at right angle to the axis of the cylinder. While the cylinder is being rotated, the load at one end of the hung fiber is caused to increase, and the load T at a time when the fiber begins to slide over the cylinder is measured. The frictional coelficient ,u. is calculated from the formula The ,u. at the time when the rotating speed is is designated as #5., and the [L at the time when the rotating speed is a peripheral speed of 90 cm./min. is designated as ad.

Generally, if the /.LS.;.Ld. is large, the fiber gives a creaky and coarse feeling, and if it is medium, the fiber gives a feeling of smoothness. On the other hand, when it is small, the fiber gives a feeling of Waxy and soft touch (Guide to Surfactants, page 167, by Isoda and Fujimoto, published by Sanyo Kasei).

In acrylic fibers, ,lLS.-/Ld. of above 0.10 gives a creaky and coarse feeling; us.;ud. of 0.07 to 0.1 gives a feeling of smoothness; and [LS.[Ld. of less than 0.07 gives a waxy and soft feeling.

Table 1 below shows the values of ,uS.,u.d. measured with respect to some kinds of fibers.

waxy and soft feel. The X-ray measurement indicated no meridian interference at 20=21.

EXAMPLE 2 Example 1 was repeated except that the ratio of acrylonitrile/stearyl acrylate/ sodium allylsulfonate was changed to 93.6/6.0/0.4 mole percent. A solution of the obtained copolymer was wet-spun in a 55% aqueous solution of dimethyl sulfoxide, drawn to 6 times the original length, washed with water, and dried to thereby form fibers having adenier of 10. The obtained filaments had a tenacity of 2.4 g./d. and an elongation of 50%. It was confirmed by a phase contrast microscopic observation that the stearyl acrylate was polymerized in block form. The fibers, when measured by the X-ray method described in the specification, had an I.R. of 0.47, and a [.LS.,U.d. value of 0.060, and possessed a wool-like feel.

When the above procedure was repeated except that the ratio of acrylonitrile/stearyl acrylate/sodium allylsulfonate was changed to 98.1/ 1.5/0.4 mole percent, the resulting fibers had an X-ray interference intensity ratio of 0.21 and a ,uS.,u.d. value of 0.098, showing inability to give a waxy and soft feeling. When the acrylonitrile/ stearyl acrylate/sodium allylsulfonate was changed to 87.6/12.0/0.4 mole percent, the resulting fibers had an X-ray interference intensity ratio of 0.78 and a ns.;td. value of 0.016, showing a remarkably waxy and soft feeling. The filaments became gluey, showing a tenacity of 1.2 g./d. and an elongation of TABLE 1 Type of fibers: pLS.,uCl. 30 EXAMPLE 3 W001 0.048 Example 1 was repeated except that each of octyl acry- Nylon 0.079 late (C lauryl acrylate (C cetyl acrylate (C and Ordinary acrylic fibers Above 0.100 stearyl acrylate (C was used as the higher alkyl acry- Rayon 0.085 late, and the deniers of the fibers were varied as indicated in the following Table 2. The results are as follows:

TABLE 2 X-ray inter- Tenacity Elongaference (grams/ tion intensity Denier denier) (percent) sd ratio Polymerization Cs 3.13 3.10 35 0.108 0 Homogeneous.

C12. 3. 2. 94 37 0.086 0. 28 Heterogeneous at the outset. and homogeneous with the passage of time.

0 3. 04 2.88 40 0.070 0.37 Heterogeneous.

C18.-- 3.27 2.70 0.052 0.58 Do.

Now, the invention will be described by the following non-limitative examples.

EXAMPLE 1 Acrylonitrile (92.6 mole percent), 7.0 mole percent of stearyl acrylate and 0.4 mole percent of sodium allylsulfonate were polymerized while stirring in a polymerization vessel in dimethyl sulfoxide in the presence of a20- bisisobutyronitrile in an amount of 0.01 mole/liter for 30 hours at a temperature of C. The total monomer concentration in the reaction mixture was 3.5 mole/ liter. The yield of the obtained polymer was about 96%. The copolymer solution was wet-spun into a aqueous solution of dimethyl sulfoxide, drawn to 6 times the original length, washed with water, and dried to thereby form fibers having a denier of 6. The obtained fibers had a tenacity of 2.7 g./d., and an elongation of 44%. It was confirmed by a phase contrast microscopic observation that the stearyl acrylate was polymerized in the form of block. The fibers, when measured by an X-ray as mentioned before, had an interference intensity ratio of 0.58, and a ,uS.p.Cl. value of 0.038. They exhibited a wool-like waxy and soft feel.

COMPARATIVE EXAMPLE 1 Example 1 was repeated except that dimethyl formamide was used in place of the dimethyl sulfoxide. A homogeneous solution-polymerization took place, and the resulting fibers had a ,us.-,ud. value of 0.115, showing no The X-ray diffraction photographs of the obtained filaments are shown in FIG. 3 in which A, B, C and D correspond respectively to C C C and C EXAMPLE 4 A copolymer solution (B) was prepared by reacting 79.6 mole percent of 'acrylonitrile, 20.0 mole percent of stearyl acrylate and 0.4 mole percent of sodium allylsulfonate under the same conditions as employed in Example 1. On the other hand, a solution (A) of this. polymer was prepared as follows: 95.6 mole percent of acrylonitrile, 4.0 mole percent of methyl acrylate and 0.4 mole percent of sodium allylsulfonate were polymerized in dimethyl sulfoxide for 40 hours at 40 C. in the presence of 0.01 mole/ liter of azobisisobutyronitrile as a polymerization catalyst. The yield of the obtained polymer was 98%.

The solution (A) and solution (B) were mixed so that the stearyl acrylate might be 6 mole percent based on the total amount of the polymers, and the mixture was extruded into a 55% aqueous solution of dimethyl sulfoxide so that the final monofilament denier might be 6. The extruded fibers were drawn to 6 times the original length, washed with water, and dried. The obtained fibers had a tenacity of 3.2 g./d. and an elongation of 35%, and possessed a waxy and soft feeling and luster. The fiber also had an X-ray interference intensity ratio of 0.60 and a ,uS.-,ud. value of 0.024. 

